Technical Abstract:
Some nuts and seeds are among the highest natural sources of vitamin E in the US food supply. In its chief function as an antioxidant, vitamin E prevents free radical reactions, which is important in the protection of cells from oxidative damage. Vitamin E has been associated with reduced risk of certain cancers such as colon, bladder, and prostate. Recent studies have focused on effects of gamma-tocopherol as well as alpha-tocopherol. While there are eight forms of vitamin E, alpha-tocopherol is the only form currently used to estimate the Dietary Reference Intake (DRI) for vitamin E. The other forms are absorbed and may have other functions, but are not converted to alpha-tocopherol in the body. The Recommended Dietary Allowance (RDA) for alpha-tocopherol is 15 mg/day for adults. According to NHANES 2001-2002, more than 90% of adults do not meet the Estimated Average Requirement of 12 mg/day. Nuts and seeds are often cited as good sources of vitamin E. USDA has recently updated tocopherol values in several nuts and seeds in the USDA National Nutrient Database for Standard Reference (SR). Findings indicate 1 oz. portions of almonds, hazelnuts, and sunflower seeds provide greater than 20% of the RDA for vitamin E; and brazilnuts and pine nuts provide between 10 and 20% of the RDA. One-ounce portions of cashews, macadamias, pecans, pistachios, black and English walnuts, flaxseed, and sesame seeds all provide between 1 and 4% of the RDA. The highest nut and seed sources of gamma-tocopherol are black walnuts (28 mg/100g), pecans (24 mg/100g), pistachios (22 mg/100g), and English walnuts and flaxseed (20 mg/100g). These tocopherol values are derived from data from USDA studies, as well as the food industry and the scientific literature. Keeping SR up-to-date allows researchers to more accurately estimate nutrient intake, thus enabling them to more effectively study the relationships between diet and disease.